1. Field of the Invention
The present invention relates to a semi-cured product, a cured product and a method for producing these, and to an optical component, a curable resin composition and a compound.
2. Background Art
An imaging module is used in cameras, video cameras, camera cell-phones, TV telephones, camera intercoms, etc. Recently, the optical system for use in such image modules is especially required to be downsized. Downsizing optical systems may bring about a serious problem of chromatic aberration in those optical systems.
Glass heretofore used as a material in optical systems can realize various necessary optical characteristics and is excellent in environmental tolerance, but has a problem in that the workability thereof is poor.
As opposed to this, a resin cured product that is inexpensive as compared with a glass material and is excellent in workability has become used in optical components. There is known a method of adding various additives to a curable resin composition to change the properties of the cured products, and recently, it has become known to make a material composition have an increased refractive index and a reduced Abbe's number and therefore to make the composition highly dispersible for chromatic aberration correction.
Here, as a monomer for use in a curable resin composition for producing optical components, a compound having a fluorene skeleton has been generally used for the reason of high refractivity thereof.
For example, Patent Reference 1 describes a (meth)acrylate compound having a 9,9-bisphenylfluorene skeleton, saying that the compound can provide a high-refractivity composition usable as an optical material.
Patent Reference 2 describes a method for producing alcohols, epoxies and (meth)acrylates having a fluorene skeleton, saying that the method can provide compounds that are colored very little. Patent Reference 2 discloses (meth)acrylates having a 9,9-bisphenylfluorene skeleton, and (meth)acrylates having a 9,9-bisnaphthylfluorene skeleton.
However, Patent Reference 1 and Patent Reference 2 do not describe a method of reducing the Abbe's number of a cured product when a fluorene skeleton-having monomer.
On the other hand, Patent Reference 3 describes a technique of burr reduction in molding to increase the good-quality ratio of molded products by semi-curing a composition containing an alicyclic structure-having (meth)acrylate monomer and a non-conjugated vinylidene group-containing compound. However, Patent Reference 3 has no description of suggesting use of a monomer having an aromatic ring structure. In addition, Patent Reference 3 does not describe a method of reducing the Abbe's number of cured products.
On the other hand, Patent Reference 4 describes a technique of providing an optical material having a small Abbe's number by using a polyester polymer that contains, as one copolymerization component therein, an alcohol having a fluorene skeleton.